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2021 Greenhouse Buyers Guide

With food security being a big concern these days with COVID-19, interest in our Do It Yourself (DIY) greenhouse kits is at an all time high.  These kits are also super fun projects to do with your family at home during the pandemic, since no special tools or experience is required to assemble them.  However, there are many factors to consider when buying a greenhouse, such as snow loads in your area, wind and sun exposure as well as proper ventilation. These factors can determine if you will need a clear glazed polycarbonate panel, or a light diffusing twin wall panel or a more insulating cover.

Did you know that the insulation value of a 2 layer inflated 6 mm poly greenhouse cover has roughly the same R 2 value (measure of heat retention) as a 10 mm thick polycarbonate greenhouse?

Mythos Polycarbonate Greenhouse

For example, for high snow areas, we may suggest at least a 6 mm to 10 mm thick polycarbonate panel for the roof and walls, or a double-walled 6 mm poly insulated high tunnel.  If you are growing fruit trees, you may need more height in your greenhouse so a gothic peak high tunnel greenhouse would make more sense than a wider round one.  Are you looking at 3 season growing to extend your season, or year-round? You may also wish to review our article on greenhouse foundation options.

First you need to consider which of the two main categories of greenhouses you need. For typical backyard growing for your family, we suggest a polycarbonate and aluminum frame greenhouse like our best selling Glory, Bella GothicGrand Gardener or Prestige greenhouses.  For larger farms or commercial needs, you will want to considering looking at custom made high tunnel cold frame greenhouses. We also sell ground coverings, exterior 6 mil poly rolls and anti-condensation 5 mil poly for preventing mildew inside your greenhouse.  We even sell mini apartment sized greenhouse options like the Plant Inn.

Hobby vs Commercial Greenhouses
Hobby greenhouses are typically at most 6 or 8 feet wide by up to 20 to 24 feet long on average.  Our greenhouses typically have a base 6x8 or 8x8 kit, and offer 4 foot extensions for length. Door heights also range from 70 inches to 74 inches and peak heights from 80 inches to 110. These greenhouses can be used year-round as 4 season shelters for your veggies and plants. These are made from aluminum or hardened resin frames with near unbreakable polycarbonate panels ranging in thickness from 1 mm clear to 10 mm for diffused light, and typically 2 feet wide.

To install a hobby size greenhouse, you need to consider how to maximize sun exposure for the kind of plants or veggies you are planning to grow.  You will need to clear a patch of level ground and consider drainage and irrigation as well as what kind of foundation you will need. You may choose to add paving stones, a slab of concrete or even just embed some pressure treated 4x4s in the ground where the frame sits. 

We can generally deliver these greenhouses in usually a week or so from our Mississauga warehouse to anywhere in Canada (pickup options are available).  During Spring peak season, you may see some out of stock or backordered items like the Bella, Glory, Prestige or the Plant Inn greenhouses.  We also provide some 12 wide x 20 to 24 foot long fabric hoop-houses from our Brampton warehouse which are ready to go kits. 

Need More Than 8x20?
If you want to feed multiple families or have larger growing needs, then you should consider our steel tube cold-frame greenhouses (cold-frame means that they don't require heating, but this depends on your region).  They can be as wide as 38 feet and as long as 100 feet and come in round or arch/gothic shapes. You will receive a few boxes of tubes (very by diameter based on width of greenhouse by 1 5/8" to 2 3/8").  You will also receive brackets and purlins (cross braces of steel that keep the ribs 4 feet apart) to attach the greenhouse arches/ribs together. 

High Tunnel Coldframe Hoop House Greenhouse

You may choose to get a patented Luminate cover included with C-channel and wiggle wire to attach it to the frame (C-channel allows for customization of side vents). Often starter plants or veggies need a clear poly with more light, and mature crops benefit from a diffused fabric cover for better heat and moisture retention and less temperature swings. You may also substitute 1 layer of 6 mm plastic at no extra charge.

High Tunnel Cold Frame Greenhouse Grizzly Shelter

Note that the clear light poly (6mm or 5mm) is ideal for growing starters, and the Luminate diffused light fabric is best for added insulation but less light for mature plants.  The diffused fabric cover insulates better and reduces extreme temperate swings, and uses less water.  The clear 6 mm poly adds heat quickly and boosts photosynthesis in early growing plants and veggies.

Note that since these greenhouse high tunnel steel frames are custom made in the US, and then shipped to Brampton, they take 6 to 8 weeks average for production and delivery in Canada. To add year-round insulation, you may want to consider a double layer of our 6 mm poly covering with an inside 5 mm layer of our Thermax anticondensation poly. Note, you would have to typically buy/install your own fan to keep it inflated.

Hobby Greenhouse DIY Kits
Our best selling greenhouses in terms of volume are our line of Palram hobby polycarbonate greenhouses.  This is a 50 Year old Israeli company that essentially invented bullet-proof glass for the military, and holds patents for near-bullet proof polycarbonate. They are the #1 manufacturer of hobby greenhouses in Canada and we are proud to be authorized dealers for them. They also provide lots of popular accessories, such as temperature sensitive roof vent openers, side louvre vents, irrigation and trellis kits, shade cloth, steel benches, shelvers and more.  When you add your greenhouse to your cart, you will be presented with many accessory options to choose from. Some models like the Glory include self-opening roof vents for example, and others like the Bella do not.

What Thickness of Panels Do I Need?
Clear panels are often thinner (1 mm) and let more light through.  Thicker panels are twin-walled and diffuse light to prevent "plant burn" and overheating. Twin walled thicker panels also add R-value insulation to your greenhouse if you choose to heat it over the winter. A 10 mm thick wall will have an R-value of around 2, and a 4 mm will be around R1. These hobby size Palram greenhouses are designed to be used 4 seasons a year, but read on for more on snow loads and wind ratings and warranties to be sure you get the right one for your area. Generally polycarbonate which is 6 mm and thicker will withstand a good amount of snow year-round.

See our assortment of polycarbonate greenhouses below by panel thickness;

 Thickness Model Warranty Snow/Wind
1 mm Harmony (1 mm walls & roof) 5 Year 15 psf / 90 kmh
1 to 4 mm

Hybrid (1 mm walls, 4 mm roof)
Balance (1 mm walls, 4 mm roof)
Garden Chalet (1 mm walls, 4 mm roof)

5 Year 15 psf / 90 kmh
4 mm Mythos (4 mm walls/roof)
Essence (4 mm walls/roof)
5 Year 15 psf / 90 kmh
6 mm Bella (6 mm walls/roof)
Grand Gardener (6 mm walls, 4 mm roof)
EcoGrow (6 mm walls, 4 mm roof)
Prestige (6 mm walls, 4 mm roof, accessories included) 
5 Year
(7 Year EcoGrow & Prestige)
20 psf / 100 kmh
10 mm Oriana (10 mm walls,1 mm roof)
Glory (10 mm walls/roof, accessories included)

10 Year (Glory only)
25 psf / 120 kmh


How Easy Are They to Assemble?
People often ask how long they take to assemble and how easy is it. Typically a 8x8 greenhouse like the Bella takes 2 people most of a day to assemble. This includes unboxing, assembling the frame, attaching the doors and vents and high fives. This can vary to it being a weekend project or longer for larger 8x20 greenhouses and does not include leveling a foundation (see further below for more on that).  Yes, there are a lot of parts with the frame, and lots of nuts and bolts to tighten, so it can be detailed and time-consuming work, especially if you are doing this alone.  It's a great family or group activity to knock off this project in a weekend and see the fruits of your labour by Monday! :)

What Kind of Foundation Do I Need?
For hobby size greenhouses, you basically need to prepare a flat, level foundation to set your greenhouse on.  Most people like a floor of soil, dirt, gravel, or paving stones. Using pressure treated wood, a concrete slab or paving stones is best to keep it level.  You may want to make only a wood or stone/cement perimeter to sit the frame on top of, and have a floor of soil for your crops. 

For example, a foundation U of 4x4 pressure treated wood embedded an inch or two into the ground is common, with dirt/soil in the middle.  Remember, you need a flat foundation otherwise your greenhouse can "rack" and the door will not close! Each kit includes lag bolts to secure the frame to your foundation.  You can also substitute wood screws to attach the frame to your pressure treated lumber base. For very high wind areas, we also have anchor kits that strap over top of your greenhouse.

Commercial High Tunnel Greenhouses
Commercial hoop houses, high tunnel or cold-frame greenhouses (the same thing) can be up to 38 feet wide and 15'3" high (round) or 34 feet wide and 12' high for arched or gothic shapes.  They include 30 inch anchor tubes that you drive ideally 20 inches into the ground, and then slide rib tubes into them.  Brackets attach cross braces (purlins) to ensure the ribs stay upright and are solid. End panels come "framed" for optional door and vent openings. Vents can be provided as accessories.   Our high tunnel steel greenhouse frames are made with US steel, and shipped from Brampton Ontario to anyway in Canada.

Click here for more high tunnel product information and brochures.

Please contact us at 1 833 GET GRIZ or via email here with any questions. 


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